Changes in Accumulated Other Comprehensive Income by Component (Detail) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Apr. 02, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income before reclassification	$ 38	$ 111
Amounts reclassified from other comprehensive income	0	0
Net current-period other comprehensive income	38	111
Ending balance	76,586
Foreign currency
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	343	452
Other comprehensive income before reclassification	34	67
Amounts reclassified from other comprehensive income	0	0
Net current-period other comprehensive income	34	67
Ending balance	377	519
Unrealized holding gains on available-for-sale investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(22)	(40)
Other comprehensive income before reclassification	4	44
Amounts reclassified from other comprehensive income	0	0
Net current-period other comprehensive income	4	44
Ending balance	(18)	4
Accumulated other comprehensive income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	321	412
Other comprehensive income before reclassification	38	111
Amounts reclassified from other comprehensive income	0	0
Net current-period other comprehensive income	38	111
Ending balance	$ 359	$ 523